This invention relates in general to a fabrication process and more specifically, to a process for heat treating a flexible electrostatographic imaging member.
Flexible electrostatographic belt imaging members are well known in the art. Typical electrostatographic flexible belt imaging members include, for example, photoreceptors for electrophotographic imaging systems and electroreceptors or ionographic imaging members for electrographic imaging systems. These belts are usually formed by cutting a rectangular sheet from a web, overlapping opposite ends, and welding the overlapped ends together to form a welded seam.
Flexible electrophotographic imaging member belts are usually multilayered photoreceptors that comprise a substrate, an electrically conductive layer, an optional hole blocking layer, an adhesive layer, a charge generating layer, and a charge transport layer and, in some embodiments, an anti-curl backing layer. One type of multilayered photoreceptor comprises a layer of finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. U.S. Pat. No. 4,265,990 discloses a layered photoreceptor having separate charge generating (photogenerating) and charge transport layers. The charge generating layer is capable of photogenerating holes and injecting the photogenerated holes into the charge transport layer.
Although excellent toner images may be obtained with multilayered belt photoreceptors, it has been found that as more advanced, higher speed electrophotographic copiers, duplicators and printers were developed, cracking of the charge transport layer and/or welded seam was encountered during cycling or when less durable materials are used. Since cracks in the photoreceptor surface cause print defects in the final copy, their appearance shortens the belt service life. However, seam cracking creates a deposition site where toner, carrier, paper debris, and dirt accumulate and eventually cause premature cleaning blade failure during photoreceptor belt machine cycling.
There is also a great need for long service life flexible belt photoreceptors in compact imaging machines that employ small diameter support rollers for photoreceptor belt systems operating in a very confined space. Small diameter support rollers are also highly desirable for simple, reliable copy paper stripping systems which utilize the beam strength of the copy paper to automatically remove copy paper sheets from the surface of a photoreceptor belt after toner image transfer. Unfortunately, small diameter rollers, e.g. less than about 0.75 inch (19 mm) diameter, raise the threshold of mechanical performance criteria to such a high level that photoreceptor belt charge transport layer and/or seam failure due to induced bending stress can become unacceptable for multilayered belt photoreceptor applications. Regarding welded seam failure, the welding operation causes a seam "splash" of melted material to form at the seam, the splash having an exposed edge which forms a 90.degree. angle where it contacts the surface of the charge transport layer. Under dynamic fatiguing conditions, the junction between the splash edge and the charge transport surface layer provides a focal point for stress concentration and becomes a point of failure in the mechanical integrity of the belt. Dynamic fatigue at this stress concentration point facilitates tear initiation through the charge transport layer. This tear then propagates through the weak charge generating layer/adhesive layer interfacial link to produce local seam delamination.
Also, in liquid development systems, induced bending stress coupled with contact with liquid developers accelerates cracking of the charge transport layer and/or welded seam. Frequent photoreceptor delamination has a serious impact on the versatility of a photoreceptor and reduces its practical value for automatic electrophotographic copiers, duplicators and printers.
Although the foregoing was discussed in terms of an electrophotographic imaging belt, they problems described equally applicable to electrographic imaging belts.